/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2005 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package clojure.asm.commons;

import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;

import clojure.asm.ClassAdapter;
import clojure.asm.ClassVisitor;
import clojure.asm.FieldVisitor;
import clojure.asm.MethodVisitor;
import clojure.asm.Opcodes;

/**
 * A {@link ClassAdapter} that adds a serial version unique identifier to a
 * class if missing. Here is typical usage of this class:
 * <p/>
 * <pre>
 *   ClassWriter cw = new ClassWriter(...);
 *   ClassVisitor sv = new SerialVersionUIDAdder(cw);
 *   ClassVisitor ca = new MyClassAdapter(sv);
 *   new ClassReader(orginalClass).accept(ca, false);
 * </pre>
 * <p/>
 * The SVUID algorithm can be found <a href=
 * "http://java.sun.com/j2se/1.4.2/docs/guide/serialization/spec/class.html"
 * >http://java.sun.com/j2se/1.4.2/docs/guide/serialization/spec/class.html</a>:
 * <p/>
 * <pre>
 * The serialVersionUID is computed using the signature of a stream of bytes
 * that reflect the class definition. The National Institute of Standards and
 * Technology (NIST) Secure Hash Algorithm (SHA-1) is used to compute a
 * signature for the stream. The first two 32-bit quantities are used to form a
 * 64-bit hash. A java.lang.DataOutputStream is used to convert primitive data
 * types to a sequence of bytes. The values input to the stream are defined by
 * the Java Virtual Machine (VM) specification for classes.
 * <p/>
 * The sequence of items in the stream is as follows:
 * <p/>
 * 1. The class name written using UTF encoding.
 * 2. The class modifiers written as a 32-bit integer.
 * 3. The name of each interface sorted by name written using UTF encoding.
 * 4. For each field of the class sorted by field name (except private static
 * and private transient fields):
 * 1. The name of the field in UTF encoding.
 * 2. The modifiers of the field written as a 32-bit integer.
 * 3. The descriptor of the field in UTF encoding
 * 5. If a class initializer exists, write out the following:
 * 1. The name of the method, &lt;clinit&gt;, in UTF encoding.
 * 2. The modifier of the method, java.lang.reflect.Modifier.STATIC,
 * written as a 32-bit integer.
 * 3. The descriptor of the method, ()V, in UTF encoding.
 * 6. For each non-private constructor sorted by method name and signature:
 * 1. The name of the method, &lt;init&gt;, in UTF encoding.
 * 2. The modifiers of the method written as a 32-bit integer.
 * 3. The descriptor of the method in UTF encoding.
 * 7. For each non-private method sorted by method name and signature:
 * 1. The name of the method in UTF encoding.
 * 2. The modifiers of the method written as a 32-bit integer.
 * 3. The descriptor of the method in UTF encoding.
 * 8. The SHA-1 algorithm is executed on the stream of bytes produced by
 * DataOutputStream and produces five 32-bit values sha[0..4].
 * <p/>
 * 9. The hash value is assembled from the first and second 32-bit values of
 * the SHA-1 message digest. If the result of the message digest, the five
 * 32-bit words H0 H1 H2 H3 H4, is in an array of five int values named
 * sha, the hash value would be computed as follows:
 * <p/>
 * long hash = ((sha[0] &gt;&gt;&gt; 24) &amp; 0xFF) |
 * ((sha[0] &gt;&gt;&gt; 16) &amp; 0xFF) &lt;&lt; 8 |
 * ((sha[0] &gt;&gt;&gt; 8) &amp; 0xFF) &lt;&lt; 16 |
 * ((sha[0] &gt;&gt;&gt; 0) &amp; 0xFF) &lt;&lt; 24 |
 * ((sha[1] &gt;&gt;&gt; 24) &amp; 0xFF) &lt;&lt; 32 |
 * ((sha[1] &gt;&gt;&gt; 16) &amp; 0xFF) &lt;&lt; 40 |
 * ((sha[1] &gt;&gt;&gt; 8) &amp; 0xFF) &lt;&lt; 48 |
 * ((sha[1] &gt;&gt;&gt; 0) &amp; 0xFF) &lt;&lt; 56;
 * </pre>
 *
 * @author Rajendra Inamdar, Vishal Vishnoi
 */
public class SerialVersionUIDAdder extends ClassAdapter{

/**
 * Flag that indicates if we need to compute SVUID.
 */
protected boolean computeSVUID;

/**
 * Set to true if the class already has SVUID.
 */
protected boolean hasSVUID;

/**
 * Classes access flags.
 */
protected int access;

/**
 * Internal name of the class
 */
protected String name;

/**
 * Interfaces implemented by the class.
 */
protected String[] interfaces;

/**
 * Collection of fields. (except private static and private transient
 * fields)
 */
protected Collection svuidFields;

/**
 * Set to true if the class has static initializer.
 */
protected boolean hasStaticInitializer;

/**
 * Collection of non-private constructors.
 */
protected Collection svuidConstructors;

/**
 * Collection of non-private methods.
 */
protected Collection svuidMethods;

/**
 * Creates a new {@link SerialVersionUIDAdder}.
 *
 * @param cv a {@link ClassVisitor} to which this visitor will delegate
 *           calls.
 */
public SerialVersionUIDAdder(final ClassVisitor cv){
	super(cv);
	svuidFields = new ArrayList();
	svuidConstructors = new ArrayList();
	svuidMethods = new ArrayList();
}

// ------------------------------------------------------------------------
// Overriden methods
// ------------------------------------------------------------------------

/*
	 * Visit class header and get class name, access , and intefraces
	 * informatoin (step 1,2, and 3) for SVUID computation.
	 */

public void visit(
		final int version,
		final int access,
		final String name,
		final String signature,
		final String superName,
		final String[] interfaces){
	computeSVUID = (access & Opcodes.ACC_INTERFACE) == 0;

	if(computeSVUID)
		{
		this.name = name;
		this.access = access;
		this.interfaces = interfaces;
		}

	super.visit(version, access, name, signature, superName, interfaces);
}

/*
	 * Visit the methods and get constructor and method information (step 5 and
	 * 7). Also determince if there is a class initializer (step 6).
	 */
public MethodVisitor visitMethod(
		final int access,
		final String name,
		final String desc,
		final String signature,
		final String[] exceptions){
	if(computeSVUID)
		{
		if(name.equals("<clinit>"))
			{
			hasStaticInitializer = true;
			}
		/*
					 * Remembers non private constructors and methods for SVUID
					 * computation For constructor and method modifiers, only the
					 * ACC_PUBLIC, ACC_PRIVATE, ACC_PROTECTED, ACC_STATIC, ACC_FINAL,
					 * ACC_SYNCHRONIZED, ACC_NATIVE, ACC_ABSTRACT and ACC_STRICT flags
					 * are used.
					 */
		int mods = access
		           & (Opcodes.ACC_PUBLIC | Opcodes.ACC_PRIVATE
		              | Opcodes.ACC_PROTECTED | Opcodes.ACC_STATIC
		              | Opcodes.ACC_FINAL | Opcodes.ACC_SYNCHRONIZED
		              | Opcodes.ACC_NATIVE | Opcodes.ACC_ABSTRACT | Opcodes.ACC_STRICT);

		// all non private methods
		if((access & Opcodes.ACC_PRIVATE) == 0)
			{
			if(name.equals("<init>"))
				{
				svuidConstructors.add(new Item(name, mods, desc));
				}
			else if(!name.equals("<clinit>"))
				{
				svuidMethods.add(new Item(name, mods, desc));
				}
			}
		}

	return cv.visitMethod(access, name, desc, signature, exceptions);
}

/*
	 * Gets class field information for step 4 of the alogrithm. Also determines
	 * if the class already has a SVUID.
	 */
public FieldVisitor visitField(
		final int access,
		final String name,
		final String desc,
		final String signature,
		final Object value){
	if(computeSVUID)
		{
		if(name.equals("serialVersionUID"))
			{
			// since the class already has SVUID, we won't be computing it.
			computeSVUID = false;
			hasSVUID = true;
			}
		/*
					 * Remember field for SVUID computation For field modifiers, only
					 * the ACC_PUBLIC, ACC_PRIVATE, ACC_PROTECTED, ACC_STATIC,
					 * ACC_FINAL, ACC_VOLATILE, and ACC_TRANSIENT flags are used when
					 * computing serialVersionUID values.
					 */
		int mods = access
		           & (Opcodes.ACC_PUBLIC | Opcodes.ACC_PRIVATE
		              | Opcodes.ACC_PROTECTED | Opcodes.ACC_STATIC
		              | Opcodes.ACC_FINAL | Opcodes.ACC_VOLATILE | Opcodes.ACC_TRANSIENT);

		if((access & Opcodes.ACC_PRIVATE) == 0
		   || (access & (Opcodes.ACC_STATIC | Opcodes.ACC_TRANSIENT)) == 0)
			{
			svuidFields.add(new Item(name, mods, desc));
			}
		}

	return super.visitField(access, name, desc, signature, value);
}

/*
	 * Add the SVUID if class doesn't have one
	 */
public void visitEnd(){
	// compute SVUID and add it to the class
	if(computeSVUID && !hasSVUID)
		{
		try
			{
			cv.visitField(Opcodes.ACC_FINAL + Opcodes.ACC_STATIC,
			              "serialVersionUID",
			              "J",
			              null,
			              new Long(computeSVUID()));
			}
		catch(Throwable e)
			{
			throw new RuntimeException("Error while computing SVUID for "
			                           + name, e);
			}
		}

	super.visitEnd();
}

// ------------------------------------------------------------------------
// Utility methods
// ------------------------------------------------------------------------

/**
 * Returns the value of SVUID if the class doesn't have one already. Please
 * note that 0 is returned if the class already has SVUID, thus use
 * <code>isHasSVUID</code> to determine if the class already had an SVUID.
 *
 * @return Returns the serial version UID
 * @throws IOException
 */
protected long computeSVUID() throws IOException{
	ByteArrayOutputStream bos = null;
	DataOutputStream dos = null;
	long svuid = 0;

	try
		{
		bos = new ByteArrayOutputStream();
		dos = new DataOutputStream(bos);

		/*
					 * 1. The class name written using UTF encoding.
					 */
		dos.writeUTF(name.replace('/', '.'));

		/*
					 * 2. The class modifiers written as a 32-bit integer.
					 */
		dos.writeInt(access
		             & (Opcodes.ACC_PUBLIC | Opcodes.ACC_FINAL
		                | Opcodes.ACC_INTERFACE | Opcodes.ACC_ABSTRACT));

		/*
					 * 3. The name of each interface sorted by name written using UTF
					 * encoding.
					 */
		Arrays.sort(interfaces);
		for(int i = 0; i < interfaces.length; i++)
			{
			dos.writeUTF(interfaces[i].replace('/', '.'));
			}

		/*
					 * 4. For each field of the class sorted by field name (except
					 * private static and private transient fields):
					 *
					 * 1. The name of the field in UTF encoding. 2. The modifiers of the
					 * field written as a 32-bit integer. 3. The descriptor of the field
					 * in UTF encoding
					 *
					 * Note that field signatutes are not dot separated. Method and
					 * constructor signatures are dot separated. Go figure...
					 */
		writeItems(svuidFields, dos, false);

		/*
					 * 5. If a class initializer exists, write out the following: 1. The
					 * name of the method, <clinit>, in UTF encoding. 2. The modifier of
					 * the method, java.lang.reflect.Modifier.STATIC, written as a
					 * 32-bit integer. 3. The descriptor of the method, ()V, in UTF
					 * encoding.
					 */
		if(hasStaticInitializer)
			{
			dos.writeUTF("<clinit>");
			dos.writeInt(Opcodes.ACC_STATIC);
			dos.writeUTF("()V");
			} // if..

		/*
					 * 6. For each non-private constructor sorted by method name and
					 * signature: 1. The name of the method, <init>, in UTF encoding. 2.
					 * The modifiers of the method written as a 32-bit integer. 3. The
					 * descriptor of the method in UTF encoding.
					 */
		writeItems(svuidConstructors, dos, true);

		/*
					 * 7. For each non-private method sorted by method name and
					 * signature: 1. The name of the method in UTF encoding. 2. The
					 * modifiers of the method written as a 32-bit integer. 3. The
					 * descriptor of the method in UTF encoding.
					 */
		writeItems(svuidMethods, dos, true);

		dos.flush();

		/*
					 * 8. The SHA-1 algorithm is executed on the stream of bytes
					 * produced by DataOutputStream and produces five 32-bit values
					 * sha[0..4].
					 */
		byte[] hashBytes = computeSHAdigest(bos.toByteArray());

		/*
					 * 9. The hash value is assembled from the first and second 32-bit
					 * values of the SHA-1 message digest. If the result of the message
					 * digest, the five 32-bit words H0 H1 H2 H3 H4, is in an array of
					 * five int values named sha, the hash value would be computed as
					 * follows:
					 *
					 * long hash = ((sha[0] >>> 24) & 0xFF) | ((sha[0] >>> 16) & 0xFF) <<
					 * 8 | ((sha[0] >>> 8) & 0xFF) << 16 | ((sha[0] >>> 0) & 0xFF) <<
					 * 24 | ((sha[1] >>> 24) & 0xFF) << 32 | ((sha[1] >>> 16) & 0xFF) <<
					 * 40 | ((sha[1] >>> 8) & 0xFF) << 48 | ((sha[1] >>> 0) & 0xFF) <<
					 * 56;
					 */
		for(int i = Math.min(hashBytes.length, 8) - 1; i >= 0; i--)
			{
			svuid = (svuid << 8) | (hashBytes[i] & 0xFF);
			}
		}
	finally
		{
		// close the stream (if open)
		if(dos != null)
			{
			dos.close();
			}
		}

	return svuid;
}

/**
 * Returns the SHA-1 message digest of the given value.
 *
 * @param value the value whose SHA message digest must be computed.
 * @return the SHA-1 message digest of the given value.
 */
protected byte[] computeSHAdigest(final byte[] value){
	try
		{
		return MessageDigest.getInstance("SHA").digest(value);
		}
	catch(Exception e)
		{
		throw new UnsupportedOperationException(e);
		}
}

/**
 * Sorts the items in the collection and writes it to the data output stream
 *
 * @param itemCollection collection of items
 * @param dos            a <code>DataOutputStream</code> value
 * @param dotted         a <code>boolean</code> value
 * @throws IOException if an error occurs
 */
private void writeItems(
		final Collection itemCollection,
		final DataOutputStream dos,
		final boolean dotted) throws IOException{
	int size = itemCollection.size();
	Item items[] = (Item[]) itemCollection.toArray(new Item[size]);
	Arrays.sort(items);
	for(int i = 0; i < size; i++)
		{
		dos.writeUTF(items[i].name);
		dos.writeInt(items[i].access);
		dos.writeUTF(dotted
		             ? items[i].desc.replace('/', '.')
		             : items[i].desc);
		}
}

// ------------------------------------------------------------------------
// Inner classes
// ------------------------------------------------------------------------

static class Item implements Comparable{

	String name;

	int access;

	String desc;

	Item(final String name, final int access, final String desc){
		this.name = name;
		this.access = access;
		this.desc = desc;
	}

	public int compareTo(final Object o){
		Item other = (Item) o;
		int retVal = name.compareTo(other.name);
		if(retVal == 0)
			{
			retVal = desc.compareTo(other.desc);
			}
		return retVal;
	}
}
}
